1. Field of the Invention
The present invention relates to a system for loading products of sheet glass, and more particularly to a loading system for loading a number of glass sheet products such as automotive window glass sheets onto a pallet.
2. Description of the Relevant Art
Glass sheet products such as automotive window glass sheets are loaded as a horizontal stack on a pallet after a certain fabrication process. Thereafter, the stacked glass sheet products on a pallet are transferred, together with the pallet, to a next process. When loading glass sheet products onto a pallet, it is general practice to place interleaving sheets between the glass sheet products for preventing the glass sheet products from being damaged due to direct contact with each other. Such interleaving sheets are normally made of paper. Where glass sheet products are rear window glass sheets printed with silver paste in a pattern of defrosting heating wires, such a silver paste pattern would tend to be transferred to intervening sheets. One solution has been to fit packings over the peripheral edges of rear window glass sheets, rather than employing interleaving sheets.
For placing an interleaving sheet between window glass sheets, the interleaving sheet is put on the upper surface of a glass sheet that has been conveyed horizontally before the glass sheet is loaded onto a pallet. Thereafter, the glass sheet is loaded onto the pallet. Since the manual procedure for putting an interleaving sheet on a glass sheet is poor in efficiency, there has been developed an apparatus for automatically putting an interleaving sheet on a glass sheet. In such an automatic apparatus, the uppermost one of a stack of interleaving sheets is attracted and lifted by a plurality of suction cups. After the interleaving sheet has been moved to a desired position, it is gripped by clamps, and then released from the suction cups. The interleaving sheet is moved over a glass sheet by moving the clamps, where the interleaving sheet is unclamped to fall onto the glass sheet. The automatic interleaving sheet putting apparatus is of a higher production rate than the manual procedure. There has also been employed an apparatus for automatically loading a glass sheet product onto a pallet because a manual loading process is low in efficiency. The glass product loading apparatus has suction cups for lifting a glass sheet product lying horizontally and loading the glass sheet onto a pallet, the suction cups communicating with a vacuum suction device. Rear window glass sheets with silver paste printed on their upper surfaces are not suitable for being loaded onto a pallet by such an automatic loading apparatus. Therefore, in practice, a glass sheet product with an interleaving sheet put thereon is loaded onto a pallet by such an automatic loading apparatus.
In the above automatic loading apparatus, the glass sheet product is attracted by the suction cups through the interleaving sheet. Therefore, there are limitations on the material of the interleaving sheet that can be used, and there is a possibility for the glass sheet product to be not sufficiently attracted by the suction cups of the loading apparatus. This problem manifests itself especially when the glass sheet product is curved.
The interleaving sheet putting apparatus is required to attract at least the four corners and center of an interleaving sheet in order to reliably lift the interleaving sheet while maintaining the flat shape thereof. Therefore, the suction mechanism is of necessity large in size with the result that the interleaving sheet putting apparatus is also large in size. When attracting the uppermost interleaving sheet, an interleaving sheet therebeneath may also be attracted, resulting in an unwanted consumption of interleaving sheets. Where a glass sheet product is curved to a relatively large extent, an interleaving sheet may not properly drop onto the glass sheet product.
In the automatic loading apparatus, a glass sheet product is released from the suction cups without concern over the gap between the glass sheet product and the preceding glass sheet product that has been loaded on the pallet, as shown in FIG. 19 of the accompanying drawings, which is a plan view of the pallet. The glass sheet product G is loaded onto the pallet 300 such that the lower edge of the glass sheet product G will fit into one of grooves 303 defined at equal intervals in a pair of spacers 302 extending parallel to each other and fixed to a bottom plate 301 of the pallet 300. Unless care were taken to position glass sheet products G parallel to each other, the lower edges of the sheet products G might not fit properly in the respective grooves 303. For example, the lower edge of a newly loaded glass sheet product G may fit in grooves 303 out of parallel to the previously loaded glass sheet products G with one groove 303 in one of the spacers 302 being left empty between the newly loaded glass sheet product G and the previously loaded glass sheet products G.
The present invention has been made in an effort to effectively eliminate the various problems with the conventional system for loading glass sheet products such as automotive window glass sheets.